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The Greenland Ice Sheet is a leading contributor to global sea‐level rise because climate warming has enhanced surface meltwater runoff. Melt rates are particularly sensitive to air temperatures due to feedbacks with albedo. The primary melt‐albedo feedback, fluctuation of seasonal snowlines, however, is determined not only by melt but also by antecedent snowfall which could delay the onset of dark glacier ice exposure. Here we investigate the role of snowfall versus air temperatures on ice sheet melt‐albedo feedbacks using satellite remote sensing and atmospheric reanalysis data. We find several lines of evidence that snowline fluctuations are driven primarily by air temperatures and that snowfall is a secondary control. First, standardized linear regressions indicate that the timing of glacier ice exposure is nearly twice as sensitive to air temperatures than antecedent snowfall. Second, in 74% of the ablation zone by area, winter snowfall rates are not significantly correlated with winter air temperatures. This relationship implies that ice sheet melt due to climate warming is unlikely to be compensated by higher snowfall rates in the ablation zone. Third, we find no significant change in snowfall rates in the ablation zone during our 1981–2021 study period. Our findings demonstrate that snowfall is unlikely to reduce future ice sheet melt and that ice sheet meltwater runoff should be accurately predicted by air temperatures. Although given the importance of melt‐albedo feedbacks, ice sheet models that parameterize albedo or are coupled with regional climate models are likely to provide the most accurate projections of mass loss. Plain Language Summary: The Greenland Ice Sheet is currently losing mass because rates of mass loss (mainly due to surface meltwater runoff and iceberg discharge into the ocean) are higher than rates of mass gain (mainly due to snowfall). As the climate warms, rates of mass loss are expected to increase non‐linearly because rising air temperatures darken the surface, leading to more solar energy absorption, and more melting. The main process responsible for surface darkening is the exposure of dark glacier ice due to Greenland's seasonally evolving snowline. The position of the snowline is determined not only by summer melt but also by the thickness of the snowpack that accumulates during winter. In this study, we investigated whether summer melt or snowpack thickness was more important for determining the timing of glacier ice exposure using satellite remote sensing and climate model outputs. We found that the glacier ice exposure is much more sensitive to air temperatures than snowfall and that snowfall did not change in the ablation zone during the 1981–2021 study period. Our findings imply that snowfall is unlikely to reduce ice sheet mass loss and that meltwater runoff from the ice sheet should be accurately predicted by air temperatures. Key Points: We investigate the extent to which antecedent snowfall versus summer air temperatures controls melt‐albedo feedbacksWe find that melt‐albedo feedbacks are primarily driven by air temperatures and that antecedent snowfall is of secondary importanceWe find little evidence that snowfall will compensate enhanced ice sheet melt due to climate warming [ABSTRACT FROM AUTHOR]

The Community Earth System Model version 2.1 (CESM2.1) is used to investigate the evolution of the Greenland ice sheet (GrIS) surface mass balance (SMB) under an idealized CO2 forcing scenario of 1% increase until stabilization at 4× pre‐industrial at model year 140. In this simulation, the SMB calculation is coupled with the atmospheric model, using a physically based surface energy balance scheme for melt, explicit calculation of snow albedo, and a realistic treatment of polar snow and firn compaction. By the end of the simulation (years 131–150), the SMB decreases with 994 Gt yr−1 with respect to the pre‐industrial SMB, which represents a sea‐level rise contribution of 2.8 mm yr−1. For a threshold of 2.7‐K global temperature increase with respect to pre‐industrial, the rate of expansion of the ablation area increases, the mass loss accelerates due to loss of refreezing capacity and accelerated melt, and the SMB becomes negative 6 years later. Before acceleration, longwave radiation is the most important contributor to increasing energy for melt. After acceleration, the large expansion of the ablation area strongly reduces surface albedo. This and much increased turbulent heat fluxes as the GrIS‐integrated summer surface temperature approaches melt point become the major sources of energy for melt. Plain Language Summary: The Greenland ice sheet (GrIS) is the largest freshwater reservoir in the Northern Hemisphere, with the potential of raising sea levels with 7.1 m if fully melted. Here, we investigate the evolution of the GrIS under elevated levels of CO2 in a model with an advanced and coupled surface mass balance (SMB; the difference between mass gain and mass loss at the ice sheet surface) calculation. By the end of our simulation, the global mean temperature increases with 5.3 K, contributing to a sea‐level rise rate of 2.8 mm yr−1 from the GrIS surface. At a global temperature increase of 2.7 K, the rate of mass loss from the GrIS accelerates due to a darker ice sheet surface and much increased atmospheric temperatures over the GrIS. Key Points: GrIS surface mass loss accelerates for a global warming of 2.7 K through increased surface melt and loss of refreezing capacityLongwave radiation is the main contributor to melt increase before acceleration; albedo and turbulent fluxes add major contributions afterAnthropogenic‐forced atmospheric circulation changes (North Atlantic Oscillation and Greenland blocking index) partially reduce melt [ABSTRACT FROM AUTHOR]